1. Field of the Invention
This invention relates to catalyst compositions useful for the cracking or conversion of hydrocarbon feedstocks containing vanadium and other contaminating metals which have a deleterious effect upon the activity and selectivity of the catalyst.
The invention is also directed to the process of preparing such catalyst compositions.
2. Prior Art
It is widely recognized that metal contaminants such as notably vanadium present in heavy petroleum-derived hydrocarbon feedstocks react with the active components of crystalline zeolite catalysts and destroy their crystalline structure, leading to severely reduced catalytic activity. It has been proposed to use various compounds such as typically alkaline earth metal compounds to passivate or immobilize vanadium and other metal contaminants deposited on the catalyst as disclosed in for example Japanese Laid-Open Patent Publications 61-149241 and 62-38242.
The alkaline earth metal compounds are known for their good ability to render metal contaminants inert, but have the problem that the alkaline earth metal dispersed in an inorganic oxide matrix tends to mobilize during the course of catalytic cracking reaction and cause a zeolite such as a crystalline aluminosilicate zeolite to decline in its thermal stability and undergo destruction of its crystalline structure, or further tends to be incorporated by ion exchange into the zeolite thereby inviting considerable decrease in the octane number of catalytically cracked gasoline products. Furthermore, some of the alkaline earth metals admixed with an inorganic oxide matrix precursor in the preparation of a crystalline aluminosilicate zeolite catalyst are prone to elute and ion-exchange with the zeolite or react with the precursor to adversely affect the physical properties and performance of the resultant catalyst.